Letter: More thoughts about metallic hydrogen (1)

From David Holdsworth, Settle, North Yorkshire, UK

Michael Brooks makes the case for hydrogen existing as a metal by pointing out its position in the periodic table at the head of the group of alkali metals (4 January, p 43).

All elements in this column have a single valence, or outer shell, electron. When this is delocalised and produces electrical conductivity in an alkali metal, there are still electrons in inner shells around the nucleus. This means a stable metallic lattice can form.

Hydrogen, which has only one electron, would be left with a naked proton, so a stable lattice would be much harder to form.

We can also put this element on the other side of the periodic table, at the top of the group of non-metallic elements that require just a single electron to form a complete outer electron “shell” – the halogens.

Metallic hydrogen may be as unusual as a G-clamp with a left-hand thread, as shown in the illustration with the article.